Why do you want to buy
PR ?
Surely you would want to be higher up in Google for you keywords... rather than having
PR?
Forget
PR, and make how high you are in Google your only metric... then buy links from related sites in your industry, but make them look natural. No sidebar or footer links, and dont bother using the link brokers. Dont buy links from sites that are dodgy.
Get the links in the content where its most natural to do so... if there's nowhere natural you can get a link from, pay them to write an article about you, or your niche, and get them to include a link...
Don't bother with getting links on links pages... and dont focus on recipricol links. Some are good, but they'll come naturally over time, with non competitors in the industry maybe, or business partners, blog friends, manufacturers etc.
Email each site you think is good enough with a unique straight forward email.
Hi,I'm XXX from XXX. I'm currently building links for our website and
I'll pay you $100 a year for a link HERE.
Thanks
XXX
You'll get a lot of sites responding to straight forward emails like that.